Method and apparatus for signaling the release of a persistent resource

ABSTRACT

A method and apparatus for signaling the release of a persistent resource in long term evolution (LTE) are disclosed. An indication of the release of a downlink (DL) persistent resource is received by a wireless transmit receive unit (WTRU) from an evolved Node-B (eNB) via a physical downlink control channel (PDCCH). A positive acknowledgement (ACK) is transmitted by the WTRU which denotes that the indication has been received. The PDCCH or a medium access control (MAC) CE may be used by the eNB to signal the indication. At least one bit may be added to contents of the PDCCH to signal whether the PDCCH is for DL persistent or dynamic resource allocation. The DL persistent resource is then released and an indication that the DL persistent resource has been released is transmitted.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/410,988 filed on Mar. 2, 2012, which is a continuation of U.S. patentapplication Ser. No. 12/405,573 filed on Mar. 17, 2009, which claims thebenefit of U.S. Provisional Application No. 61/038,921 filed Mar. 24,2008, the contents of each of which are incorporated by referenceherein.

TECHNICAL FIELD

This application is related to wireless communications.

BACKGROUND

The basis for uplink (UL) and downlink (DL) scheduling is dynamicscheduling. In a long term evolution (LTE) wireless communicationsystem, scheduling information is transmitted during transmission timingintervals (TTIs) to a wireless transmit/receive unit (WTRU) via aphysical downlink control channel (PDCCH). It has been agreed by radioaccess network (RAN) working groups (i.e., RAN2) to supportsemi-persistent scheduling for the DL and the UL in LTE. Forsemi-persistently scheduled WTRUs in a TTI, a DL/UL grant does not needto be sent for initial data transmission. The only exception is when anevolved Node-B (eNB) wants to override the persistent resourceassignment, which by definition should be infrequent. Otherwise, thesole purpose of a DL/UL persistent resource assignment is lost. As anoptimization for voice over Internet protocol (VoIP), persistentscheduling is used for both DL and UL, where the resource for theinitial transmissions is persistently allocated and the resources forthe hybrid automatic repeat request (HARQ) retransmissions isdynamically allocated.

Persistent resource scheduling is configured and controlled, (e.g.,turned on and off), by radio resource control (RRC) signaling. Forinstance, persistent resource scheduling may be controlled based on theperiodicity of a resource allocation. HARQ processes that are used forpersistent scheduling are provided using RRC signaling.

The exact timing, resources, and transport format parameters used for apersistent DL assignment are sent on a layer 1 (L1)/layer 2 (L2) controlchannel as a normal DL assignment. For example, an HARQ processidentification (ID) may be used to indicate that the assignment shouldbe stored. If the persistent DL assignment is missed, which occurs whenthere is no acknowledgment or non-acknowledgment (NACK), then an evolvedNode-B (eNB) resends the assignment.

For VoIP service, the release of semi-persistent resources in both theDL and UL is important. Both explicit resource release and implicitresource release have been previously discussed, but there has yet to bea decision made as to the implementation of these features.

Furthermore, there is a need to clarify potential new signalings tosupport the release of a persistent resource using both explicit andimplicit methods, procedures for either explicit or implicit persistentresource release, a failure case handling when persistent resourcerelease signaling is lost or corrupted, new signaling for the activationof the persistent resource, and new signalings for the reconfigurationof the persistent resource allocation.

There exists the need for new signalings and rules for the activation,deactivation, reconfiguration, and release of UL and DL persistentresources in LTE systems.

SUMMARY OF THE INVENTION

A method and apparatus for signaling the release of a persistentresource in LTE are disclosed. An indication of the release of a DLpersistent resource is received by a WTRU from an eNB via a PDCCH. Apositive acknowledgement (ACK) is transmitted by the WTRU which denotesthat the indication has been received. A PDCCH signaling or a mediumaccess control (MAC) control element (CE) may be used by the eNB tosignal the indication. At least one bit may be added to contents of thePDCCH to signal whether the PDCCH is for DL or UL persistent or dynamicresource allocation. The DL or UL persistent resource is then releasedand an indication that the DL or UL persistent resource has beenreleased is transmitted.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawingwherein:

FIG. 1 shows a wireless communication system that is configured tosignal the release of a persistent resource.

DETAILED DESCRIPTION

When referred to hereafter, the terminology “wireless transmit/receiveunit (WTRU)” includes but is not limited to a user equipment (UE), amobile station, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment.

When referred to hereafter, the terminology “evolved Node-B (eNB)”includes but is not limited to a base station, a site controller, anaccess point (AP), or any other type of interfacing device capable ofoperating in a wireless environment.

FIG. 1 shows a wireless communication system 100 including a WTRU 105and an eNB 110, which communicate over a physical downlink controlchannel (PDCCH) 115 and a physical uplink control channel (PUCCH) 120.The WTRU 105 includes a transmitter 125, a receiver 130, a processor 135and a buffer 140. The eNB 110 includes a transmitter 145, a receiver 150and a processor 155.

An indication of the release of a DL persistent resource is transmittedby the transmitter 145 in the eNB 110, and is received by the receiver130 of the WTRU 105 via the PDCCH 115. The transmitter 125 in the WTRU105 transmits an ACK to the ENB 110 which denotes that the indicationhas been received. The buffer 140 is used to store a DL assignment andDL transmitted data. A PDCCH or a MAC CE may be used by the eNB 110 tosignal the indication. At least one bit may be added to contents of thePDCCH to signal whether the PDCCH is for DL persistent or dynamicresource allocation. The DL persistent resource is then released and anindication that the DL persistent resource has been released istransmitted by the transmitter 125 in the WTRU 105.

Explicit DL Persistent Resource Release

A method for signaling the release of a DL persistent resource usingexplicit signaling is disclosed. When explicit signaling is used tosignal the release of a DL persistent resource from the eNB 110 to theWTRU 105, as shown in FIG. 1, either a PDCCH or a MAC CE may be used tosignal the release of the DL persistent resource.

If a PDCCH 115 is used for explicit signaling, then one bit is added inthe PDCCH 115 to signal whether the PDCCH 115 is for DL persistent ordynamic resource allocation. The one bit added to the PDCCH 115 may alsosignal the WTRU 105 to use separate cell radio network temporaryidentifiers (C-RNTIs), or to use a reserved value of some other field,such as a transmit power control (TPC) field.

Then, the WTRU 105 transmits an ACK/NACK to the eNB 110 to confirm thereceipt of the PDCCH release signaling. Alternatively, after the WTRU105 releases the DL persistent resource, the WTRU 105 transmits anindication to the eNB 110 to confirm the successful release of the DLpersistent resource. With respect to the release of an UL persistentresource, the eNB 110 implicitly confirms the resource release by a lossof detection of the previously allocated resource.

A field on a PDCCH not used for persistent allocation may be used toindicate the release of DL or UL persistent resource. For example, twobits in a TPC field may be used, in which “00” indicates the release ofa DL persistent resource, and two bits “01” in the TPC field may be usedto indicate the release of a UL persistent resource.

A special MAC CE may be used to signal the release of a DL and ULpersistent resource. For example, the two bits “00” in a MAC CE mayindicate the explicit release of the DL persistent resource, and the twobits “01” may indicate the explicit release of the UL persistentresource. The number of bits in the MAC CE may vary, and a differentdigit permutation may be predefined for DL and UL persistent resourcerelease.

If the WTRU 105 does not successfully receive the PDCCH or blinddetection does not indicate any new DL voice packets in preconfiguredTTIs for M times, then the WTRU 105 may release the DL persistentresource. The TTIs are used for persistent reception. This method may becharacterized as a WTRU implicit resource release. Depending on whetherthe WTRU 105 can still receive DL dynamic traffic, the WTRU 105 shouldfollow the rules to enter either a long or short discontinuous reception(DRX) cycle. After release of the DL persistent resource, it is optionalwhether the WTRU 105 transmits an indication to eNB 110, informing theeNB 110 of the autonomous release of the DL persistent resource. Theindication may be transmitted using the next available periodic PUCCH,or through a new UL MAC CE.

Alternatively, when the WTRU 105 receives a first DL systemidentification number (SID) from the eNB 110 after the WTRU 105 entereda talk-spurt duration state, the WTRU 105 releases the DL persistentresource because the WTRU 105 determines that a talk-spurt durationstate is finished. The WTRU 105 may then optionally transmit anindication to the eNB 110, indicating the release of the DL persistentresource.

Implicit DL Persistent Resource Release

A method for signaling the release of a DL persistent resource usingimplicit signaling is disclosed. The rules for the WTRU's implicitrelease of the DL persistent resource is similar to the failure handlingwhen an explicit DL persistent resource signal is not received. However,there are differences in the WTRU rules for handling an implicit DLpersistent resource release.

If the WTRU 105 does not successfully receive the PDCCH 115, and/orblind detection does not indicate any new DL voice packets in thepreconfigured TTIs for M times, then the WTRU 105 may release the DLpersistent resource. Depending on whether the WTRU 105 can still receiveDL/UL dynamic traffic, the WTRU 105 should follow the rules to entereither long or short DRX cycle. When the WTRU 105 changes from a longDRX cycle to a short DRX cycle, or changes from a short DRX cycle to along DRX cycle, then the WTRU 105 should report the change to the eNB110 within the on-duration (or active time) of a new DRX cycle so thatthe eNB 110 knows the change of WTRU DRX cycle and avoids transmittingDL signaling in a wrong cycle's on-duration.

After the implicit release of the DL persistent resource, the WTRU 105may then optionally transmit an indication to eNB 110 indicating theautonomous release of the DL persistent resource. This indicationconfirms the release of the DL persistent resource. The indication maybe transmitted using the next available periodic PUCCH or through a newUL MAC CE.

Alternatively, when the WTRU 105 receives a first DL SID from the eNB110 after the WTRU's talk-spurt duration, the WTRU 105 releases the DLpersistent resource and enters a silent period because the WTRU 105determines that a talk-spurt duration state is finished. The WTRU 105may then optionally transmit an indication to the eNB 110 indicating therelease of the DL persistent resource. The indication may be transmittedusing the next available periodic PUCCH, or through a new UL MAC CE.

Explicit UL Persistent Resource Release

A method for signaling the release of an UL persistent resource usingexplicit signaling is disclosed.

After the WTRU 105 transmits an empty buffer (or padding) buffer statusreport (BSR) to the eNB 110 which indicates that there is no UL data forthe WTRU 105 to transmit to the eNB 110, an indication of the explicitrelease of an UL persistent resource is transmitted from the eNB 110using the PDCCH. The transmission of the indication of the explicit ULpersistent resource release may be generated multiple times to decreasethe probability of unsuccessful reception at the WTRU 105. The WTRU 105may optionally provide feedback with an ACK/NACK. The transmission ofthe indication of the explicit UL persistent resource release may bepiggybacked or multiplexed with other MAC PDUs. The indication of theexplicit UL persistent resource release may be transmitted using thenext available PDCCH or through a new DL MAC CE.

After the UL persistent resource is successfully received by the WTRU105, the WTRU 105 may then transmit an indication to eNB 110 toacknowledge the release of the UL persistent resource.

Alternatively, confirmation of the release of the UL persistent resourceis accomplished implicitly when the eNB 110 fails to detect subsequentUL transmissions on the UL persistent resource.

When the explicit UL persistent resource release signal is transmittedfrom the eNB 110 to the WTRU 105, there may be failure cases in whichthe indication is lost or in error. To handle the failure cases, thefollowing methods are disclosed.

If the eNB 110 does not receive a NACK from the WTRU 105 aftertransmitting the explicit release of the UL persistent resource signal,then the eNB 10 transmits the explicit release of the UL persistentresource signal again until a maximum number of retransmissions isreached. At the expected subframe when the WTRU 105 should receive theexplicit release of the UL persistent resource signal from the eNB 110,after the WTRU 105 transmits the empty BSR, if the WTRU 105 does notreceive any feedback from the eNB 110, then the WTRU 105 releases the ULpersistent resource autonomously if the WTRU 105 does not have any newUL VoIP packets in the buffer after N TTIs.

Alternatively, the WTRU 105 immediately releases the UL persistentresource when the WTRU 105 does not receive any feedback from the eNB110 after transmitting the empty BSR.

Alternatively, if the WTRU 105 transmits the empty BSR and does notreceive an explicit release of the UL persistent resource signal fromthe eNB 110, then the WTRU 105 does not release the UL persistentresource until there is an UL SID available. Then, the WTRU 105 sends ascheduling request (SR) for SID transmission to the eNB 110, enablingthe eNB 110 to determine that the WTRU 105 transitioned from atalk-spurt duration state to a silent period. As a result, the ULpersistent resource is already autonomously release by the WTRU 105.

Alternatively, after the WTRU 105 releases the UL persistent resourceand enters a new DRX cycle, (depending on the DL/UL dynamic traffic),the WTRU 105 transmits an UL indication to the eNB 110, wherein theindication denotes the release of UL persistent resource and the startof the new DRX cycle to synchronize the WTRU 105 with the eNB 110. TheUL indication may be transmitted in the next PUCCH using physical (PHY)signaling. Alternatively, the UL indication may be in the physicaluplink shared channel (PUSCH) as a new MAC CE or radio resource control(RRC) signaling. The new MAC CE indicates the implicit release of ULpersistent resource by the WTRU 105.

Implicit UL Persistent Resource Release

A method for signaling the release of an UL persistent resource usingimplicit signaling is disclosed.

After the WTRU 105 detects that there is no more UL voice data packet,the WTRU 105 transmits an empty buffer (or padding) BSR, a PHYindication in PUCCH, or a MAC CE to the eNB 110 indicating the statuschange and immediately releases the UL persistent resource implicitly.The WTRU 105 transmits the empty buffer (or padding) BSR on Nconsecutive semi-persistent subframes.

In an alternative embodiment, the WTRU 105 transmits the empty (orpadding) BSR only once and waits for N-1 consecutive semi-persistentsubframes to determine whether there is new voice data available in abuffer. If there is no new voice data in the buffer during this period,then the WTRU 105 releases the UL persistent resource.

Alternatively, the WTRU 105 releases the UL persistent resource when theWTRU 105 has a first UL SID packet to transmit since entering thetalk-spurt state. The WTRU 105 may release the UL persistent resourcewhen the WTRU 105 has the SID packet in the buffer, after the WTRU 105sends the SR, or after the WTRU 105 transmits the first UL SID packet.

Alternatively, after the WTRU 105 releases the UL persistent resourceand enters a new DRX cycle, (depending on the DL/UL dynamic traffic),the WTRU 105 transmits an UL indication to the eNB 110, wherein theindication denotes the release of UL persistent resource and the startof the new DRX cycle to synchronize the WTRU 105 with the eNB 110. TheUL indication may be transmitted in the next PUCCH using PHY signaling.Alternatively, the UL indication may be in the PUCCH as a new MAC CE orradio resource control (RRC) signaling. The new MAC CE indicates theimplicit release of UL persistent resource by the WTRU 105.

Activation and Reconfiguration Signaling for Persistent Resource

A method for signaling the activation and reconfiguration of apersistent resource using implicit signaling is disclosed. A new fieldis added to the PDCCH 115 to indicate the start time for either DL or ULpersistent resource allocation. The new field may be in the form of astarting system frame number (SFN). Alternatively, either a DL or ULpersistent resource allocation may be triggered, without using the starttime, when a WTRU 105 successfully decodes the PDCCH 115 for persistentallocation. The DL or UL persistent resource allocation is triggeredimmediately at a next subframe or N subframes, after successfullydecoding the PDCCH 115 for persistent allocation.

For reconfiguration of both the UL and DL persistent resource, eitherthe PDCCH 115 or the MAC CE may be used, in addition to using RRCsignaling. When using the PDCCH 115 and/or MAC CE to reconfigure apersistence resource, the following may be used to reconfigure an UL orDL persistent resource.

1) If only the radio resource and transport format need to bereconfigured, then the PDCCH 115 may be used to include the new resourceand transport format (TF) information without significantly changing thePDCCH 115 content.

2) If information such as periodicity and/or at least one new HARQprocess needs to be configured with the resource and transport format,then both the PDCCH 115 and MAC CE may be used to reconfigure the newresource and TF.

3) If only periodicity and/or at least one new HARQ process needs to bereconfigured, then only the MAC CE may be used for the reconfigurationof the persistent resource.

4) A new field is added to the PDCCH 115 for the configuration orreconfiguration of the persistent resource, wherein the new fieldincludes parameters for periodicity and at least one HARQ process. Thenew field permits the PDCCH 115 to be used for the reconfiguration ofall necessary parameters including periodicity, at least one HARQprocess, exact start timing, resources, and transport format.

5) A MAC CE is used for the reconfiguration of all necessary parametersincluding periodicity, at least one HARQ process, exact start timing,resources, and transport format.

Although features and elements are described above in particularcombinations, each feature or element can be used alone without theother features and elements or in various combinations with or withoutother features and elements. The methods or flow charts provided hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable storage medium for execution by ageneral purpose computer or a processor. Examples of computer-readablestorage mediums include a read only memory (ROM), a random access memory(RAM), a register, cache memory, semiconductor memory devices, magneticmedia such as internal hard disks and removable disks, magneto-opticalmedia, and optical media such as CD-ROM disks, and digital versatiledisks (DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth.RTM. module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB)module.

What is claimed:
 1. A method implemented by a wireless transmit receiveunit (WTRU) for reconfiguring a persistent resource, the methodcomprising: the WTRU receiving a configuration for persistent resourcescheduling in a radio resource control (RRC) message sent from anevolved Node B (eNB), the configuration for persistent resourcescheduling comprising an indication of a periodicity of a persistentresource allocation; the WTRU receiving a first physical downlinkcontrol channel (PDCCH) transmission applicable to the persistentresource allocation from the eNB, wherein the first PDCCH transmissiontriggers the WTRU to activate the persistent resource allocation; andthe WTRU receiving a reconfiguration of the persistent resourceallocation via a second PDCCH transmission from the eNB, wherein thereconfiguration of the persistent resource allocation changes resourcesand transport format used for the persistent resource allocation withoutaffecting the periodicity of the persistent resource allocation.
 2. Themethod as in claim 1, wherein the persistent resource allocation is adownlink persistent resource allocation.
 3. The method as in claim 2,wherein the configuration for persistent resource scheduling furthercomprises an indication of one or more hybrid automatic repeat request(HARQ) processes to be used for the persistent resource allocation. 4.The method as in claim 3, wherein the reconfiguration of the persistentresource allocation included in the second PDCCH transmission does notchange the one or more HARQ processes to be used for the persistentresource allocation.
 5. The method as in claim 1, further comprising theWTRU activating the persistent resource allocation in the subframe inwhich the first PDCCH transmission was received based on receiving thefirst PDCCH transmission.
 6. The method as in claim 1, wherein thepersistent resource allocation is an uplink persistent resourceallocation.
 7. The method as in claim 1, further comprising the WTRUreceiving a third PDCCH transmission from the eNB, the third PDCCHtransmission comprising a release of the persistent resource allocation.8. The method as in claim 7, further comprising the WTRU transmitting apositive acknowledgment to the eNB based on receiving the third PDCCHtransmission comprising the release of the persistent resourceallocation on condition that the persistent resource allocation isapplicable to a downlink persistent resource.
 9. The method as in claim8, further comprising the WTRU refraining from transmitting a positiveacknowledgment to the eNB when receiving the third PDCCH transmissioncomprising the release of the persistent resource allocation oncondition that the persistent resource allocation is applicable to anuplink persistent resource.
 10. A wireless transmit receive unit (WTRU)comprising a processor and memory, the WTRU configured, at least inpart, to: receive a configuration for persistent resource scheduling ina radio resource control (RRC) message sent from an evolved Node B(eNB), the configuration for persistent resource scheduling comprisingan indication of a periodicity of a persistent resource allocation;receive a first physical downlink control channel (PDCCH) transmissionapplicable to the persistent resource allocation from the eNB, whereinthe first PDCCH transmission triggers the WTRU to activate thepersistent resource allocation; and receive a reconfiguration of thepersistent resource allocation via a second PDCCH transmission from theeNB, wherein the reconfiguration of the persistent resource allocationchanges resources and transport format used for the persistent resourceallocation without affecting the periodicity of the persistent resourceallocation.
 11. The WTRU as in claim 10, wherein the persistent resourceallocation is a downlink persistent resource allocation.
 12. The WTRU asin claim 11, wherein the configuration for persistent resourcescheduling further comprises an indication of one or more hybridautomatic repeat request (HARQ) processes to be used for the persistentresource allocation.
 13. The WTRU as in claim 12, wherein thereconfiguration of the persistent resource allocation included in thesecond PDCCH transmission does not change the one or more HARQ processesto be used for the persistent resource allocation.
 14. The WTRU as inclaim 10, wherein the WTRU is further configured to activate thepersistent resource allocation in the subframe in which the first PDCCHtransmission was received.
 15. The WTRU as in claim 10, wherein thepersistent resource allocation is an uplink persistent resourceallocation.
 16. The WTRU as in claim 10, wherein the WTRU is furtherconfigured to receive a third PDCCH transmission from the eNB, the thirdPDCCH transmission comprising a release of the persistent resourceallocation.
 17. The WTRU as in claim 16, wherein the WTRU is furtherconfigured to: transmit a positive acknowledgment to the eNB based onreceiving the third PDCCH transmission comprising the release of thepersistent resource allocation on condition that the persistent resourceallocation is applicable to a downlink persistent resource; and refrainfrom transmitting a positive acknowledgment to the eNB when receivingthe third PDCCH transmission comprising the release of the persistentresource allocation on condition that the persistent resource allocationis applicable to an uplink persistent resource.
 18. An evolved Node B(eNB) comprising a processor and memory, the eNB configured, at least inpart, to: transmit, to a wireless transmit receive unit (WTRU), aconfiguration for persistent resource scheduling in a radio resourcecontrol (RRC) message, the configuration for persistent resourcescheduling comprising an indication of a periodicity of a persistentresource allocation to be used by the WTRU; transmit a first physicaldownlink control channel (PDCCH) transmission applicable to thepersistent resource allocation to the WTRU, wherein the first PDCCHtransmission triggers the WTRU to activate the persistent resourceallocation; and transmit a reconfiguration of the persistent resourceallocation via a second PDCCH transmission to the WTRU, wherein thereconfiguration of the persistent resource allocation changes resourcesand transport format used for the persistent resource allocation withoutaffecting the periodicity of the persistent resource allocation.
 19. TheeNB as in claim 18, wherein the persistent resource allocation is adownlink persistent resource allocation, the configuration forpersistent resource scheduling further comprises an indication of one ormore hybrid automatic repeat request (HARQ) processes to be used for thepersistent resource allocation, and the reconfiguration of thepersistent resource allocation included in the second PDCCH transmissiondoes not change the one or more HARQ processes to be used for thepersistent resource allocation.
 20. The eNB as in claim 1, wherein thepersistent resource allocation is an uplink persistent resourceallocation, and the eNB is further configured to: transmit a third PDCCHtransmission to the WTRU, the third PDCCH transmission comprising arelease of the persistent resource allocation; and implicitly determinethat the WTRU has released the persistent resource allocation based onfailing to detect a subsequent uplink transmission from the WTRU sent inaccordance with the uplink persistent resource allocation.